Technical Abstract:
The shank fillet of channel catfish is a primary product form produced during processing and is formed by trimming the belly flap or nugget section from a boneless fillet. Belly flap meat comprises around 20 percent of the fillet weight. Belly flap meat has a fat content of about 15 percent compared to about 9 percent for the shank fillet. The fat content of the belly flap meat, which limits its shelf life and confers undesirable sensory qualities, along with the black-pigmented peritoneal membrane present on the surface of the belly flap contribute to its classification as a low-value by-product of catfish processing. Wholesale price paid for catfish belly flap meat, also known as catfish nuggets, averages about 37 percent of the shank fillet price.
A series of studies was undertaken to evaluate the potential for developing a value-added product using minced channel catfish belly flap meat. Washing of catfish mince resulted in whiter tissues or products due to the removal of blood, pigments, and water-soluble proteins; however, the presence of specs of comminuted peritoneal membrane resulted in grayish or dark areas on certain points of the product. Washing increased the moisture content from 71.5 percent to 77.9 percent while reducing mechanical hardness (19.1 N to 11.9 N), chewiness index (14.2 N to 8.83 N) and shear force (0.82 J to 0.51 J), and fat content (9.82 percent to 4.39 percent). The particle size of minced belly flap meat affected significantly textural characteristics of catfish patties cooked by dry or moist heat. As size of meat particles for patties decreased, hardness and gumminess, and color difference from fillet increased, but Kramer shear break force as well as percent cooking loss decreased. Patties cooked in an oven showed greater color difference from fillet, percent cooking loss, hardness and gumminess than those cooked in water for the same size of meat particles. Microbial transglutaminase (MTGase) and non-meat proteins (isolated soy protein, ISP and whey protein concentrate, WPC) alone and in combination were evaluated in order to improve cooking yield and textural properties in catfish patties with reduced NaCl and no phosphate. MTGase increased textural properties such as binding strength, hardness, cohesiveness, chewiness, and springiness, but decreased cooking yield of the patties. ISP increased cooking yield, but did not affect textural properties, whereas WPC did not increase cooking yield or impact textural properties of patties. The combination of MTGase and ISP significantly increased both the cooking yield and textural properties of patties. As the concentration of MTGase increased at constant ISP, the textural properties of cooked patties significantly increased, but cooking yield decreased. Catfish belly flap meat offers potential for developing one or more value-added products.